The present invention relates to an innerboot, particularly for sports shoes, made of thermoformable material.
Sports shoes, such as for example ski boots or roller skates or ice skates, are currently conventionally provided with an external structure, constituted by a shell and optionally by one or more quarters articulated thereto, which are made of rigid material. In order to increase the user's comfort, an innerboot made of soft material is usually inserted in the shell and in the quarters.
Said innerboots are conventionally produced by using thermoformable materials having a closed-cell structure and therefore being not vapor-permeable and the characteristic whereof is that they adapt very well, when heated appropriately, to the anatomy of the user's foot, offering both better comfort during sports practice and a good degree of foot securing, so as to transmit the efforts to the ski, to the wheels, or to the ice-skating blade in an optimum manner.
Said conventional innerboots, however, entail drawbacks: since the thermoformable material is not vapor-permeable, the foot sweats during the use of the sports shoe and it is not possible to expel the resulting moisture externally, thus considerably reducing user comfort.
Any provision of through holes at the walls of the innerboot would still not solve the problem, because ventilation would occur in any case only at the perforated regions, whilst the moisture would stagnate in the remaining regions.
Moreover, through holes cannot be provided extensively in the innerboot, because they would weaken it.
Moreover, during shaping, the deformation of the innerboot after heating would plug the holes, making them useless for their purpose.
U.S. Pat. No. 4,095,355 discloses an inshoe for a ski boot having, at the lateral surfaces and in a region adjacent to the malleoli, a plurality of projections adapted to produce air circulation between the inner lateral surface of the boot, which is rigid, and the outer lateral surface of the inshoe, which is soft.
This solution has been provided specifically with the purpose of varying the inshoe softness in some particular regions, such as for example the malleolar region.
Said projections should also allow a different transmission of forces from the foot to the boot and therefore to the ski according to the different deformation of the projections.
Said patent also mentions the possibility of providing the projections at the inner lateral surface of the inshoe so that said projections make contact with the user's foot.
However, this possibility, which is not shown, has drawbacks: by providing ventilation during the movement of the foot, which by compressing the projections produces a "pump effect" affecting small air pockets that form during this very movement, the relative movements of the foot with respect to the inshoe or of the inshoe with respect to the boot are observed to increase, and this is in contrast with current trends which tend to provide for optimum securing of the foot in order to achieve more direct and better control of the sports implement, such as the ski.
Moreover, the fastening of the shell and/or of the quarters of the boot certainly limits this "pump effect", because an undesired precompression of the projections would occur, thus limiting any compression of the small air pockets that form during the movement of the foot.